Three-dimensional plural display apparatus

ABSTRACT

This apparatus forms and displays sequentially a plurality of three-dimensional images. Frames from a film strip are stroboscopically selected and projected on a moving screen. The effect may be simply a comparison of two three-dimensional images. Alternatively, an illusion of motion of a three-dimensional image may be created. Safety features prevent access to rotating parts and other features protect the stroboscope from excessive and unnecessary use. A single three-dimensional image may be selected and continuously projected on the screen.

CROSS-REFERENCES

This invention is an improvement on the inventions disclosed in the U.S.patents to de Montebello, No. 3,428,393 and No. 3,462,313, and in thecopending U.S. application of Edward A. Woloshuk et al., Ser. No.86,383, filed Oct. 19, 1979, all of which are incorporated herein byreference.

BRIEF SUMMARY OF THE INVENTION

The apparatus of the de Montebello patents identified above utilize afilm strip comprising successive cross-sectional views of an object. Theframes of the film strip are arranged in the order corresponding to therelationship of the successive cross-section. The film strip is movedthrough an optical system in which the frames are successivelystroboscopically illuminated, one at a time, and the images produced bythat illumination are projected on a rotating screen of spiralcross-section, rotatable about the axis of the spiral. In amodification, the screen is made up of segments of part-cylindricalcontour, rotatable about an axis eccentric with respect to the axes ofthose contours. An observer of the rotating screen having persistence ofvision sees all of the images projected into a three-dimensional spaceand thus gets a view of a transparent solid showing the internalstructure of the object. The apparatus in de Montebello U.S. Pat. No.3,428,393 masks out part of the images along a plane perpendicular tothe planes of the successive photographs in a series, so that across-sectional image can be produced which is taken along a selectedplane perpendicular to the planes of the original photographs.

The apparatus of the Woloshuk et al. application has the furthercapability of displaying a two-dimensional image taken along the planeof any selected original photograph. It can alternatively display athree-dimensional image cut along a selected plane at either or bothends of the stack of original cross-sectional views.

The present invention improves the apparatus of the de Montebellopatents and of the Woloshuk et al. application by providing for acomparison of two or more successively presented three-dimensionalimages. In its simplest form, the apparatus presents twothree-dimensional images alternately, so that the observer can makevisual comparison of the two images. For example, the two images may beof a part of the human body in different positions. The extremes ofmovement of a ventricle and of the expansion of human lungs areillustrated. More complex forms of the present invention, using morethan two three-dimensional images, can be employed so as to give aneffect of animation, similar to that obtained in a two-dimensionalmoving picture, but with all three dimensions visible. Alternatively, asection taken along any of the three dimensions may be selected forpresentation.

The cross-sectional views representing one of two images in the propersequence are placed in a predetermined set of locations on the strip.The cross-sectional views representing the other image are placed in adifferent predetermined set of locations on the strip. The strip isplaced on an endless carrier such as a transparent drum or belt, bywhich it is moved repeatedly through the optical system. The flashing ofthe stroboscope lamp is controlled to select one set of images or theother. One set of images is illuminated for several cycles of rotationof the film strip, and the illumination is then switched to the otherset of images. The two sets of images are illuminated alternately,although the alternation may be stopped to allow continuous presentationof one image. If more than two sets of images are used, they may beilluminated in a predetermined repeated sequence, to present anappearance of motion. Again, the sequence may be stopped to present oneimage continuously.

DRAWINGS

FIG. 1 is a perspective external view of an apparatus embodying theinvention.

FIG. 2 is a fragmentary cross-sectional view taken along the lines 2--2of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view taken on the line 3--3 ofFIG. 2.

FIG. 4 is a fragmentary cross-sectional view on the line 4--4 of FIG. 2.

FIG. 5 is a fragmentary cross-sectional view on the line 5--5 of FIG. 4.

FIG. 6 shows a longitudinal cross-sectional view of a ventricle of ahuman heart in closed position.

FIG. 7 shows a longitudinal cross-sectional view of the same ventriclein the open position.

FIG. 8 shows a film strip, with a section broken away, constructed bymaking cross-sectional X-ray views taken along the lines AA, BB, CC andDD of FIGS. 6 and 7 and arranging them in the positions illustrated.

FIG. 9 shows a cross-sectional X-ray view of a human chest with thelungs contracted.

FIG. 10 shows a similar view of the same chest with the lungs expanded.

FIG. 11 shows a film strip constructed by making cross-sectional viewson the lines AA, BB, CC and DD of FIGS. 9 and 10, and arranging them inthe positions illustrated.

FIGS. 12A, 12B, 12C and 12D show four successive longitudinal sectionalviews of a ventricle in a human heart, as that ventricle moves from theclosed position shown in FIG. 12A to the open position in FIG. 12D.

FIG. 13 is a fragmentary view of a film strip showing successivecross-sections on the lettered lines AA to QQ in FIGS. 12A to 12D,arranged in alphabetical order.

FIG. 14 is a fragmentary view of a film strip used in connection withthe invention.

FIG. 15 is a wiring diagram of a stroboscope trigger control circuitused in the invention.

FIG. 16 is a wiring diagram of a timing selector circuit shown in asingle box in FIG. 13.

FIG. 17 is a wiring diagram of an interlocking circuit forming a part ofthe invention.

FIG. 18 is a wiring diagram of a power supply circuit.

FIG. 19 is a timing diagram relating to FIGS. 15-18.

FIG. 20 is a perspective view of a rotating screen in the apparatus ofFIGS. 1-5.

DETAILED DESCRIPTION FIGS. 1-5 AND 20

FIG. 1 illustrates the external appearance of the apparatus and includesa casing generally indicated at 1, having a forwardly facing slantedupper surface 1a on which there is centrally mounted a transparent dome2 through which the three-dimensional display is to be observed. Thefront wall 1b of the casing below the slanting surface 1a includes amain control panel 3 and an auxiliary control panel 4. Projecting fromthe right-hand side of the surface 1b of casing 1 are a pair ofcooperating rotatable discs 5 and 6 having respective scales 5a and 6amarked on their surfaces. A slidable door 7, shown in its closedposition, is movable rearwardly to give access to the interior of thecasing 1. The door 7 actuates a switch 8 (FIG. 2) when it is moved awayfrom its closed position. The inside of the door 7 carries a bar 9 whichengages a locking pin 10 when the door is opened a very short distancewhich is too small for a hand to enter through the door. The locking pin10 may be withdrawn by energization of a solenoid 11.

The main control panel 3 includes a frame selector activating switch 20and four frame selector switches 12, 13, 14 and 15. Each switch includesan operating handle moving along a slot adjacent a fixed scale. Digitalindicators 16, 17, 18, 19 are provided above the reflective switches 12,13, 14 and 15. These switches select from a film strip particularphotographs to be displayed, by means of apparatus described below andillustrated in FIGS. 14-18.

A master switch 23 controls the supply of power to the entire apparatus.A knurled thumb wheel 24 controls a Dove prism 65 (FIG. 2) for rotatingthe image under the dome 2. Another knurled thumb wheel 25 controls azoom lens 64 which may be used to magnify the image appearing under thedome 2. A rotatable knob 32 controls the horizontal framing of the imageby movement of photosensors 101 and 102 (see FIG. 5).

The discs 5 and 6 normally rotate independently, the disc 5 being heldstationary by a brake. When the brake is released, it is possible torotate the disc 5, either along or together with the disc 6.

FIGS. 2 and 3 illustrate the principal mechanical parts of the apparatusand their relation to the casing 1 illustrated in FIG. 1. A film strip33 (FIGS. 2 and 4) is mounted in a film holder 34 comprising atransparent hollow drum 35 at the inner surface of that drum. Atransparent locking ring 36a of substantially thinner material than thedrum 35 may be moved into the drum after the film is in place andthereafter expanded and locked to hold the film in place. The drum 35 isprovided with curved slots (not shown) cooperating with pins 36 on awheel 37 fixed on a hub 38. The pins 36 and slots form a bayonet joint.The drum 35 may alternatively be provided with apertures which canreceive spring loaded balls mounted on the wheel 37 in place of the pins36.

The hub 38 is provided with a step 38a at one end to cooperate with astep 40a on a hub 40 fixed on a shaft 41 for rotation therewith. (SeeFIG. 4). The shaft is supported by a plate 28 and a plate 43. The plate43 also serves as a mount and a heat sink for a motor 44 (See FIG. 2).

The hub 38 is apertured to receive a pair of balls 45, which are biasedby springs 46 held in place by threaded retainers 47. The balls 45cooperate with a groove 41b in the shaft 41, and releasably lock the hub38 to the shaft 41, so that the hub 38 and the film holder 34 mountedthereon can be readily removed as a unit from the shaft 41.

A pulley 50 is fixed on the shaft 41. Over the pulley 50 runs a belt 51.The belt 51 runs over another pulley 52 fixed on a shaft 53 driven bythe motor 44. The belt 51 and the pulleys 50 and 52 are provided withmating teeth, so that there can be no slippage between the film wheel 37and the shaft 53.

Rotatably mounted on the shaft 41 is an arm 39, which projectsdownwardly and carries near its lower end a U-shaped block 48 whichsupports a pair of photocells 101 and 102, inside the film holder 34,and a pair of lamps 103 and 104 located outside the film holder 34 forenergizing these photocells. The lower end of arm 39 is connected by ajoint 49 to a flexible shaft 32a connected to the framer control knob 32at the front of the casing 1. The shaft 32a has at its end a screwmember which cooperates with the joint 49 so that the arm 39 may berotated through a limited excursion about the shaft 41.

The shaft 53 has fixed thereon a projection screen 54, best seen in FIG.20, and comprising four projecting screen segments 54a of arcuatecross-section, each extending through an angle of about 90° with respectto the axis of the screen 54. The screen 54 comprises two discs 55 and57 which hold the four screen segments 54a in fixed relation to eachother. The disc 55 is fixed on the shaft 53. Each disc 55 and 57 hasfour arcuate quadrants 55a and 57a which mate with and hold the arcuatescreen segments 54a. Attached to the end of each arcuate quadrant 55a isa plate 56 which extends axially and is attached at its other end to thecorresponding arcuate quadrant 57a of disc 57. The disc 57 has a centralaperture 57b.

Light from a stroboscopic lamp 61 is projected along an optical path 88best seen in FIG. 2. Beginning at lamp 61, the optical path may betraced through a pair of condensing lenses 62, and then passes throughthe transparent drum 35 and a frame of the film strip 33. The light isthen reflected by a reflector 63 through zoom lens 64 and prism 65 toreflectors 66 and 67 to a final reflector 68 located near the centralaxis of the screen 54. Reflector 68 is located slightly to the right ofthat axis, as shown in FIG. 2. The centerline of the reflector is in aplane through that axis, which plane is generally parallel to the outerportions of the rotating screen segments 54a, as they pass under thedome 2. From the reflector 68, the image is projected directly onto asegment 54a of the screen 54. The reflector 68 is mounted on a bracket(not shown) which is mounted on the base of the casing 1 and extendsthrough the aperture 57b in the center of the plate 57. The reflectors63, 66, 67, 68 may be coated with a high reflecting coating (HR)deposited thereon by sputtering or vapor deposition, and which reflects95-98% of the light received on each surface.

The film holder 34 (FIG. 4) is rotated at a speed four times the speedof the screen drum 54, so that the entire film strip mounted on theholder 34 is projected onto each screen segment 54a. The screen drum 54rotates clockwise as viewed in FIG. 20 so that the first frame projectedon a screen 54a is viewed at the outer end or maximum radius portion ofthat screen. The subsequent frames of the film are projected on thescreen at locations of successively decreasing radii with respect to theaxis of rotation. Thus, after each flash of the lamp 61 resulting in aprojection of an image, the screen recedes slightly from the observer'seye before the next frame is projected on the screen. Thethree-dimensional effect is dependent on the persistence of vision inthe observer's eye. By moving the screen away from the observer aftereach projected image, the screen does not appear to intervent betweenthe persisting images and the new images.

The dome 2 which provides a 360° view of the image projected may betinted slightly with, for example, a gray tint and the screen segments54a may be given a similar gray tint. With such an arrangement, thecontrast between the projected images and the background is increased,so that the projected images are more readily visible to the observer.In the casing 1, should be mounted at least two cooling fans (not shown)to provide proper cooling for the lamp 61 and motor 44 described above.

FIGS. 6-8

FIGS. 6 and 7 illustrate a ventricle of a human heart, in closedposition in FIG. 6 and in open position in FIG. 7. FIG. 8 illustrates afilm strip 111 made up of successive cross-sections through theventricle of FIGS. 6 and 7. In producing any practical film strip, therewould be a large number of cross-sections taken through the ventricle atdifferent successive locations. To simplify the illustration, only twolocations are selected, one at each end of the ventricle. Thecross-section AA is taken near the narrow end of the closed ventricleand the cross-section BB is taken near the narrow end of the openventricle. Cross-section CC is taken near the wide end of the closedventricle and cross-section DD is taken near the wide end of the openventricle. The film strip 111 is shown as a fragment consisting of fourframes. Frame A is taken at the cross-section AA in FIG. 6; frame B istaken at the cross-section BB in FIG. 7. After a break in the filmindicating where the intervening cross-sections would appear in thecompleted film strip, there appears a frame C taken at the cross-sectionCC in FIG. 6 and a frame D taken at the cross-section DD in FIG. 7.

FIGS. 9-11

FIGS. 9 and 10 illustrate a pair of human lungs in the contracted andexpanded positions, respectively. FIG. 11 shows a film strip 113illustrating the manner in which the cross-sections taken on the linesAA, BB, CC and DD of FIGS. 9 and 10 are assembled in the film strip 113.

In FIG. 9, the cross-section AA is taken near the upper end of the lungwith the lungs contracted. The section BB is taken on the same plane,which appears as BB in FIG. 10, with the lungs expanded. The section CCis taken near the lower end of the lungs with the lungs contracted.Section DD is taken on the same plane with the lungs expanded. In thefilm strip 113, cross-section AA appears in frame A and cross-section BBappears in frame B. After a break in the film strip representing theintervening sections, the sections CC and DD appear in the frames C andD.

Note that in both the film strip 111 of FIG. 8 and the film strip 113 ofFIG. 11, the cross-sectional views which go to make up thethree-dimensional images are alternated. That is to say, a cross-sectiontaken from a closed ventricle is followed by a cross-section on the sameplane taken from an open ventricle. This alternation of the viewscontinues throughout the strip.

It is not absolutely necessary to the invention that the arrangement ofthe frames on the film strip be alternating. Theoretically, anyarbitrary arrangement of the two sets of cross-sectional images could beemployed. For the purposes of comparing two three-dimensional images, itis convenient to arrange the frames in alternating order. Otherarrangements could be used with equal facility providing the frameselection circuitry is coordinated with the order in which thecross-sections are arranged in the film strip.

FIGS. 12-13

These figures illustrate a modification of the invention in which fourthree-dimensional images are to be successively presented to the viewer.FIGS. 12A, 12B, 12C and 12D show four views of the ventricle 110 varyingsuccessively from a completely closed position in FIG. 12A, a partiallyopen position in FIG. 12B, a more widely open position in FIG. 12C and awide open position in FIG. 12D.

FIG. 13 shows the arrangement of cross-sectional views through theventricle 110 in the four positions of FIGS. 12A-12D as they areassembled in a film strip in accordance with the invention. The sectionsare identified alphabetically from AA to QQ in FIGS. 12A to 12D. In FIG.13, each frame is identified by a single letter corresponding to thecross-section from which it was taken in one of FIGS. 12A-12D. In FIG.13, the sections are arranged sequentially with a section from 12Afollowed by sections from FIGS. 12B, 12C and 12D on the same plane andappearing in that order. After a break in the film strip whichrepresents cross-sectional views taken on intervening planes notidentified by lines in FIGS. 12A-12D, another set of four views appear,again taken in the same order.

When the film strip of FIG. 13 is projected in the apparatus of FIGS.1-5, four three-dimensional images are successively seen. The durationof each image is controllable, and it is possible to secureapproximation of a movement in three-dimensions appearing on the screen.

FIGS. 14-15

FIG. 14 illustrates a fragment of the film strip 33 showing the usualsprocket holes 33a in one margin thereof. A reset aperture 33b is cut inthe same margin, extending between two of the sprocket holes. Thisaperture 33b serves to reset the frame counters in a manner to bedescribed below. The aperture 33b is located in the film strip 33 sothat aperture 33b is in the center of the photosensor block 48 (FIG. 4)when the last frame of the film strip 33 passes through the optical path88. Aligned with the margin of the film strip carrying the sprocketholes 33a and the reset aperture 33b are a pair of lamps 103 and 104located in photosensor block 48 on the outside of the film holder 34 inits operating position (FIGS. 4-5) and respectively cooperating withphotosensors 101 and 102 located in the photosensor block 48 on theinside of the film holder. The photosensors 101 and 102 may bephototransistors whose base leads are left unconnected. They are setapart by a circumferential distance of 1.14 cm. The sprocket holespacing is 0.76 cm. The aperture 33b is 0.12 cm long.

The strobe trigger control system of FIG. 15 counts the frames in thefilm strip by counting the holes 33a. It also counts the revolutions ofthe film holder by counting the apertures 33b. These counts are comparedwith preset counts established by the setting of manually operatedswitches 12, 13, 14, 15.

The strobe trigger control system of FIG. 15 is energized by closing theswitch 20 having movable contacts 20a and 20b to the position shown inFIG. 15. Switch 20 may be of the push-push type. In this position,contact 20a connects the output of NOR gate 125 to NAND gate 132, whichgives control of the strobe trigger 134 to the counter/comparatorcircuitry; and also, contact 20b serves to supply power to the displayindicators 16, 17, 18, 19 (FIG. 1).

The photosensors 101 and 102 respond to the light passing through thesprocket holes 33a and the reset aperture 33b. The outputs ofphotosensors 101 and 102 are connected to pulse shapers 105 and 106,respectively, so as to produce square wave outputs for the rest of thecircuitry. The output from photosensor 101 passes through timingselector 129 (FIG. 16), NAND gate 128, inverter 131, NAND gate 132 andinverter 133 to supply the pulses to the strobe trigger 134. All of theother circuitry shown in FIG. 15 controls and gates these triggerpulses.

The output of photosensor 101 also passes to a decade counter 107 whichrecords the count and converts it from binary to binary-coded-decimal(BCD) form. The BCD output of the counter 107 is transmitted to twocomparators 111 and 112. The counter 107 is a units counter and has atens output line 113 connected to a second decade counter 114 for tenshaving BCD output lines connected to two comparators 115 and 116. Thecomparison inputs of the comparators 111, 115, 112, 116 are generated bythe four frame selector switches 12, 13, 14 and 15, respectively (seeFIG. 1). The switches 12, 13, 14 and 15 control digital numericaldisplays 16, 17, 18 and 19, respectively. The positions of each of theswitches 12, 13, 14 and 15 are translated by BCD converters 121, 122,123 and 124 respectively, to BCD form and are supplied to the comparisoninputs of the comparators 111, 115, 112 and 116, respectively.

When the comparators 111 and 115 reach a count less than or equal tothat of their comparison inputs, they transmit a high output signal toone input of NOR circuit 125. This drives the output of NOR 125 low,which locks the trigger output from photosensor 101, via NAND 132, andthus turns off the strobe supply 134. Likewise, when the comparators 112and 116 reach a count greater than or equal to that of the comparisoninputs, they transmit a signal to the second input of the NOR gate 125,which similarly locks the trigger output via NAND gate 132 and turns offstrobe supply 134.

The photosensor 101 alone controls the counters 107 and 114, andprovides the ultimate trigger pulse to strobe supply 134.

The photosensor 102, while it produces an output pulse in response toeach passing sprocket hole, is arranged to rest the counters every timethe reset aperture 33b passes it. Since the distance between thesprocket holes 33a is 0.76 cm, and the distance between photosensors 101and 102 is 1.14 cm, when reset aperture 33b passes photosensors 101 and102, both will receive light simultaneously. The output of photosensor102 passes through pulse shaper 106 and is connected to one input ofNAND gate 126. The other input of NAND gate 126 is from the output ofpulse shaper 105 and hence from photosensor 101. The output of NAND gate126 is connected to one input of an inverter circuit 135 whose output isconnected to reset inputs of the decade counters 107 and 114. Thosereset inputs are high when a pulse is received simultaneously byphotosensors 101 and 102 (when reset aperture 33b passes) and reset thedecade counters to a zero count.

The output of NAND gate 126 is also connected through a wire 127 to oneinput of NAND gate 128. The other input of NAND gate 128 comes throughtiming selector 129 from pulse shaper 108, and hence from photosensor101. NAND gate 128 prevents the transmission of spurious trigger pulsesto strobe supply 134 when reset hole 33b passes photosensors 101 and102.

The output of NAND gate 128 passes through an inverter 131 to one inputof NAND gate 132. The output of NOR gate 125 is also connected toanother input of NAND gate 132 through element 8a of switch 8. When thisinput is high at +V potential (either from the +V line or the output ofNOR gate 125), control of the trigger pulse is from photosensor 101 andthe strobe supply 134 flashes strobe lamp 61 (FIG. 2). When the outputof NOR gate 125 goes low, the NAND gate 132 output stays high, and thestrobe trigger pulse from photosensor 101 is blocked and does nottrigger the strobe lamp 61.

OPERATION OF FIG. 15 Mode 1--Parallel Section Dissector OFF

If the switch 20 is set so that contact 20a is connected to +V andcontact 20b is open (not connected or N/C), the NAND gate 132 operatesas an inverter for signals from inverter 131. Display lights 16, 17, 18and 19 are off. The photosensor 101 produces an output pule in responseto each sprocket hole 33a, of which there is one for every photographicframe in the film strip 33. These pulses are passed through NAND gate128 and the NAND gate 132 and trigger the strobe lamp 61 as each framepasses the gate 94. The pulses are also transmitted to decade counter107. However, in this mode the output of counters 107 and 114 isignored. The NAND gate 128 is still operative in the circuit andprevents reset hole 33b from generating spurious pulses.

Mode 2--Parallel Section Dissector ON

If decade counters 107 and 114 are reset to zero and switch contact 20ais connected to NOR gate 125 output and switch contact 20b is in thefull line position shown, switches 12 and 13 are, for example, set tothe number 12, and switches 14 and 15 are set to the number 48, thedisplays 16, 17, 18 and 19 are ON and read "1", "2", "4" and "8",respectively.

As before, photosensor 101 produces one pulse per passage of hole 33a,which goes to decade counter 107. However, until the decade countersreach the count of 12, the output of comparator 115 is high and theoutput from comparator 116 is low. The high output from comparator 115is inverted by NOR gate 125 and this low signal is supplied to one inputof NAND gate 132, which blocks the pulses to the strobe trigger control134 until the count of 12 is reached. At that count, the output from thecomparator 115 goes low, and, since the output of comparator 116 isstill low, the output of NOR gate 12 is high. Subsequent counting pulsesfrom photosensor 101 provide the NAND gate 132 with the appropriateinput pulses and hence trigger the strobe lamp 61 once for every passingframe. The photosensor 101 continues to pulse the strobe light for everypassing frame until the comparators 112 and 116 reach the count (48) setinto the switches 14 and 15, at which time the output of comparator 116goes high. The inverted (low) output of NOR gate 125 is transmitted, asbefore, to one input of NAND gate 132 and thereby blocks the outputpulses from that gate from reaching the strobe supply, and thus stopsthe flashing of strobe lamp 61.

Thus, a selected number of frames at the beginning of the strip can beblanked out by setting the switches 12 and 13, and a selected number offrames at the end of the strip may be blanked out by setting theswitches 14 and 15.

Common to Both Modes

The reset aperture 33b is located in the film strip 33 so that it passesphotosensor block 48 (FIG. 5), when the end of the film passes theoptical path 88 (FIG. 2). When the reset aperture 33b is opposite bothphotosensors 101 and 102, both photosensors transmit pulsessimultaneously to NAND gate 126. NAND gate 126 then transmits an outputpulse through the inverter 135 to the reset inputs of counters 107 and114, resetting both counters to zero. An output pulse is alsotransmitted directly from NAND gate 126 to NAND gate 128.

The NAND gate 128 functions to block the operation of the strobe lightwhen the reset pulse is received from photosensor 102. The reason forthis is that the strobe lamp has a maximum practical operating frequencyand the flashing rate corresponding to the set speed of the motor 44 isnear that maximum. The presence of an extra trigger pulse at a higherfrequency, such as might be created by the reset apertures 33b, mightimpair the smooth, steady operation of the strobe light.

The film strip 33 commonly has about 90 frames, and the counters have acapacity of 99. It is therefore necessary to reset the counters aftereach passage of the film strip.

The positions of the photosensors 101 and 102 may be adjusted withrespect to the film wheel 34 so that the strobe light is energized atthe correct instant during the passage of the frame. The mechanism formaking this adjustment is illustrated in FIG. 5.

The film holder runs, in one embodiment of the invention, at 2000 rpm,and the projection screen wheel runs at 500 rpm.

FIG. 16

This timing selector circuit has three input terminals identifiedrespectively as 129a, 129b and 129c, and a single output terminalidentified as 129d. All the input terminals and the output terminal areconnected as shown in FIG. 15.

The sprocket hole counting pulses appear at input terminal 129a. Adouble pole double throw switch 140 in the position shown connects theinput terminal 129a directly through to the output terminal 129b. Inthat position, the apparatus projects a single three-dimensional pictureonto the screen.

In the dotted line position of switch 140, the input pulses fromterminal 129a are directed through a divider circuit 141, and thence tothe output terminal 129b. When the switch 140 is in the dotted lineposition, the strobe trigger 134 is pulsed only at alternate frames ofthe film strip. Capacitors 142 and 144 are connected to the input andoutput of divider 141 to assist in pulse shaping. The resistor 143connected to the input of that divider is a loading resistor to preventthe divider from running away when the switch 140 is in the positionshown.

Input pulses at terminals 129b and 129c are complementary, representingreset and no-reset conditions. The pulses from terminal 129b count therevolutions of the film wheel 34 and are directed through a divider 145,which divides by two and a divider 146 which divides by ten and thenceinto a BCD counter 147. The output lines of BCD counter 147 areconnected to a comparator 150. The other input lines of the comparator150 are connected to a manual BCD switch 151, by which the number ofrevolutions of the film holder are to be counted before switching fromone set of frames to the other is established. Comparator 150 produces apulse on an output line 150a whenever the count from the counter 147 isequal to the count set in the BCD switch 151. The line 150a supplies areset pulse to the counter 147 and also supplies a pulse through a line152 and a blocking diode 153, and a manual switch 154 to the input of aflip-flop 155. The Q output of flip-flop 155 is connected to one inputof a NOR gate 156. The Q output of flip-flop 155 is connected to oneinput of NOR gate 157. The other inputs of the NOR gates 156 and 157 aresupplied from the terminal 129c.

Whichever output Q or Q of flip-flop 155 is low when the not-resetsignal is received at 129c will make the output of that NOR gate highwhich will either set or reset the divider 141. These reset or not-resetpulses are refreshed with every revolution of the wheel 134. The set offrames which has been selected for illumination by the stroboscopic lampis not switched until the equal count pulse is received from thecomparator 150. Refreshing the set or reset pulse each revolution of thefilm holder is desirable to avoid the effect of any possible noise ordirt blocking the sprocket hole and the like which might result in ashift from one set of frames to the other set at and undesired time. Byopening the freeze switch 154, the operator can lock the projector sothat it displays either set of frames continuously.

FIGS. 17-18

These figures illustrate circuits for controlling the motor 44 and thesolenoid 11 which controls the lock 10. These circuits are controlled bythe main switch 123 (FIGS. 1 and 18), the door operated switch 8 and afilm interlock circuit 160.

The circuit of FIG. 15 supplies a pulse at an output terminal 161 inresponse to every passing sprocket hole. The pulses at terminal 161 aretransmitted to a retriggerable single shot circuit 162 (FIG. 17) whoseoutput line 163 is connected to one input of the film interlock 160.

Referring to FIG. 18, power is supplied from an AC supply line throughthe main switch 23 to two transformers 164 and 165. The secondary oftransformer 164 is connected to a rectifier bridge circuit 166 whoseoutput is connected through a diode 167 to an output terminal 170. Theoutput of bridge 166 is also connected directly to an output terminal171, where the potential contains a substantial ripple component. Theoutput of transformer 164 is also connected through a pair of siliconcontrolled rectifiers (SCR's) 172 and 173 whose common output isconnected to a terminal 174. The control electrodes of the rectifiers172 and 173 are connected through a transformer 175 to control inputterminals 176 and 177.

The output of transformer 165 is connected to a rectifier bridge 178whose output is connected through a voltage regulator 180 to the displaylamps 16, 17, 18 and 19, shown in FIG. 1 and to a terminal 179, whichalso appears at several locations in FIG. 17. The output of bridge 166is also connected through a voltage regulator 181 to the lamps 101 and102 which energize the phototransistors 103 and 104.

The power to the motor 44 from output terminal 174 is controlled bysignals at the terminals 176 and 177. These signals are controlled by acircuit shown in FIG. 17 which may be traced from power supply terminal179 through a resistor 182, a resistor 183, a unijunction transistor 184and diode 185. The terminals 176 and 177 are connected to the oppositeterminals of the diode 185. The control electrode of the unijunctiontransistor 184 is controlled by an optoisolator 186, which is a devicehaving a light producing element 187 such as a light emitting diode(LED) controlling a light sensitive element 188. The signals supplied bythe light sensitive element 187 are controlled by the Q output terminalof the film interlock circuit 160, and by the output of a phasecomparator 195. The Q output of circuit 160 passes through an inverter191 and a diode 192 to one terminal of the light producing element 187.The output terminal of phase comparator 195 is connected through aninverter 194 and diode 193 to the same terminal of element 187. Oneinput terminal of the phase comparator 195 is connected through aconductor 196 to the output 163 of the single shot 162. The other inputof the phase comparator 195 is connected to a voltage controlledoscillator (VCO) 197. The input of voltage controlled oscillator 197 isconnected to the slidable contact of a variable resistor 200 connectedbetween an input terminal 201 and ground.

The circuit described above maintains a constant speed of the motor 44as determined by the frequency established at the voltage controlledoscillator 197 by the setting of the variable resistor 200.

Under certain dangerous or undesirable operating conditions, motor 44 isremoved from the control of the circuit just described and istransferred to a braking circuit in which it is supplied with directelectrical energy of reverse polarity for the purpose of stopping itquickly. The conditions which produce this reverse energization of themotor are the opening of the door to get access to the film holder, orthe absence of a film in the film holder.

The door switch 8 is shown in FIG. 17 in the door open position and ismovable therefrom to a door closed position. Switch 8 has contacts 8aand 8b. In the door closed position, the contact 8b supplies power tothe circuitry 139 of the strobe lamp 61 (FIG. 2) and contact 8a throughwhich one terminal of motor 44 is connected to ground through a diode241. The circuitry 139 represents the power supply for the stroboscopelamp 61. The flashing of that lamp is determined by the pulses at thestroboscope trigger 134 (FIG. 2). Such circuitry is known in thestroboscope art.

The energizing circuit for relay 202 may be traced from an inputterminal 170 through the inlet sensitive element of an optoisolator 203,a resistor 204, a PNP transistor 205 to the winding of relay 202 andthence through contact 8a to ground. The input circuitry of optoisolator203 is controlled in response to the sprocket hole counting impulses atterminal 161 as represented by the signal on the output line 63 ofsingle shot 162. This signal passes through a retriggerable monostablecircuit 206 to one input of a NOR circuit 207, whose output is connectedto one input of a flip-flop 208. The Q output of flip-flop 208 isconnected through an inverter 209 and a resistor 210 to the input ofoptoisolator 203.

The Q output of film interlock 160 is connected through an inverter 213to a light emitting diode (LED) 214 which illuminates a signal 215having a "NO FILM" indication. The other terminal of diode 214 isconnected through a diode 216 to the door closed contact of switch 8a.That contact is also connected to the common terminal of a resistor 220and a Zener diode 221. That common terminal is connected through aninverter 222 and a diode 223 to a reset input of film interlock circuit160. That common terminal is also connected through an inverter 224 tothe other input of the NOR circuit 207 and to one input of the flip-flop208. The Q output of film interlock 160 is also connected to one inputterminal of a NOR circuit 225, whose output terminal is connectedthrough an inverter 226 to one input of a NOR circuit 227 having anoutput connected to one input of a three input NOR circuit 228. Theoutput of NOR circuit 230 is connected through an inverter 231 to theinput of an optoisolator 228 whose output controls the supply of energyto the solenoid 11 which operates the lock 10 on the door 7 (FIG. 1).

The output of inverter 224 is also connected to the other input of NORcircuit 225. The common junction of a resistor 229 and a Zener diode 235is connected through an inverter 232 to the other input of NOR circuit227. The output of inverter 232 is also connected through a diode 233 toa second input of NOR circuit 230. A third input of NOR circuit 230 isconnected to the output of inverter 224. The common junction of resistor229 and Zener diode 235 is also connected through a resistor 236 and adiode 237 to one terminal of the motor 44.

In the absence of any dangerous or undesirable condition, the motor 44will run at a speed determined by the setting of the variable resistor200. The silicon controlled rectifiers 172 and 173 are controlled byunijunction transistor 184, which is in turn controlled by the phaselocked loop including the phase comparator 195 and the voltagecontrolled oscillator 197.

When a sprocket hole detection pulse is received at terminal 161, it isrepeated by single shot 162 and compared by comparator 195 with a pulsegenerated by the voltage controlled oscillator 197. If the photocellpulse is leading, the unijunction transistor 184 is turned off to slowthe motor 8. If the pulse is lagging, it acts through the optoisolator186 and unijunction transistor 184 to speed up the motor. Thus, themotor runs at a constant speed set by the resitor 200 which iscontrolled by the setting of the screw head 199 in FIG. 1.

As long as pulses are received from the sprocket hole countingphototransistors 101 and 102, the single shot 162 holds the Q output ofinterlock 160 high and the optoisolator 186 remains under the control ofthe phase comparator 195. If the pulses stop for longer than about 0.75second, the single shot 162 changes its output state and the interlock160 acts on the optoissolator 186 to remove power from the motor 44. Ifthe film door is closed, the no-film lamp 215 will also be lighted. Oncethe NO-FILM indication is lighted, the only way to reset the system andstart it again is to open and close the door so as to reset the switch8. When this is done, the interlock 160 receives a pulse from themicroswitch contact 8a and the motor gets a short energization. If nopulse is received from the sprocket hole detectors, the single shot 162will again cut off the output of interlock 160, and the motor will stopagain. If there is film on the wheel with sprocket holes to be detected,this short energization is more than sufficient to start the photocelldetecting pulses from the film holder.

When the door is closed, the inverter 224 has a low input and thus ahigh output. This high output acts to reset the flip-flop 208 and alsoensures that the output of NOR gate 207 remains low. The monostablecircuit 206 receives the sprocket hole counting pulses from single shot162. As long as the interval between the sprocket hole pulses is suchthat the frequency is greater than about 50 Hertz (correspondng to about5 rpm of the screen), the single shot 162 will continue timing and theoutput of the monostable circuit 206 will remain high. When flip-flop208 is in the reset mode, its output is high and the optoisolator 203remains off and the relay coil 202 which it controls through transistor205 also remains off. If the door is opened sufficiently to engage theswitch 8, contact 8a connects the input of inverter 224 to groundthrough resistor 217, so that the output of inverter 224 goes low,removing the reset input from the flip-flop 208. The set input alsoremains low due to the high signal from monostable circuit 206. Thus,when the door starts to open, the motor power is removed by the actionof the flip-flop 208. The relay coil 202 is energized and the motor isconnected to a reverse polarity circuit. This dynamic braking mode ofoperation of the motor continues until the monostable circuit 206changes state, indicating that the motor has slowed the rotating screento about 5 rpm. Then the NOR circuit 207 output goes low and the setinput of the flip-flop 208 goes high, the optoisolator 203 turns on,deenergizing the relay coil and terminating the dynamic braking mode ofoperation.

The diode 241 is connected in the circuit of motor 44 to prevent theinverter 224 from going into a high state when the door is open byfinding a low impedance path through the motor supply filter andcapacitor.

The NOR circuit 230 checks three inputs. The input from the interlock160 goes low when the circuit has stopped generating pulses in responseto the sprocket holes for longer than 0.75 seconds. The input frominverter 224 goes low when the film door is opened far enough so thatthe microswitch 8 is tripped. The signal from inverter 232 goes low whenthe relay 202 returns to the de-energized condition, indicating that themotor is coasting or stopped. These three signals are negative logicanded by way of the NOR circuit 230. when all three conditions are true,the output of the circuit 230 acts by way of the optoisolator 232 toenergize the solenoid 11, and release the lock.

If the single shot 162 should start running through its cycle again, asmight happen, for example, when the light beam from the photocell isinterrupted, and again completed as the film holder is being removed andreplaced, the flip-flop 230 will simply lose its positive set and boththe set and reset inputs of that flip-flop will remain low. Thus nochange of state will occur and the solenoid will remain energized andthe lock will remain unlocked.

Should the door 7 subsequently be closed so that the switch 8 resets tothe closed position (the lower position as shown in the drawing), theinverter 224 output will go high and this will remove the set input fromthe flip-flop 230 and apply a high signal to the reset, thus causing thesolenoid to release and relock the door.

The NOR circuit 230 comprises three inputs connected through NOR gatesto the input of a flip-flop. In order to trigger the flip-flop, allthree inputs of the NOR gate must be in their low condition.

Should there be an error in the relay 202 (e.g., a sticking contact)that causes it to remain in the reverse braking mode, the inverter 224will never go low and the solenoid 11 will never become energized arerelease the lock.

If the film holder should be omitted, or the film itself unloaded andnever reloaded, the motor will receive an initial supply of power asmentioned previously. During the time that the initial pulse is receivedby the film interlock circuit 160, the Q output of that circuit will gohigh preventing the door from opening until power is removed. The doorlatch solenoid is de-energized and the door is locked at this time. Whenthe film interlock 160 reaches the end of its cycle, the Q output willgo low and the solenoid 11 will be energized and release the lock. Sincethe initial energization of the motor is only enough to give the motor asmall velocity (less than 5 rpm), there is no hazard if the operatorshould open the door at this point. Indeed, at that speed, the motorcomes to a complete stop within the time it takes the operator to openthe door.

In the power supply circuit of FIG. 18, note that the voltage regulators180 and 181 that supply power to the logic circuit and the photocellenergizing lamps operate off a second transformer 165 separate from themotor transformer 164. This prevents any motor noise or current surgesfrom the motor circuit from entering the logic with possible erroneousresults.

The apparatus of the invention has other medical uses besides the onesexplained in detail above. For example, it can compare past X-raypictures or other photographs with more recent ones of the same subject.Another example, one view might be taken to emphasize bone structure anda different one to emphasize soft tissue or injected contrast material.It might also be used to compare an overall view with a highly magnifiedview.

The apparatus also has industrial uses. For example, it might be used tocompare a perfect specimen with a new specimen just produced.

The circuitry described in detail in FIG. 16 is adapted for use with thefilm strips shown in FIGS. 8 and 11, where only two three-dimensionalviews are being compared. If it is desired to change to a system forcomparing four three-dimensional views as shown in FIGS. 12 and 13, thedivide by two circuit 143 would be replaced by a divide by four circuit.A four pulse counter would be inserted in the set line between the NORcircit 157 and the set input of the divide by four circuit.

The invention is not limited to a particular sequence of the sets ofpictures in the film strip. For example, the alternating arrangementshown in FIGS. 6-10 for two images being compared could be replaced byan arrangement in which all of the pictures in one set were arranged insequence and followed by all of the pictures in the other set insequence. The circuitry would have to be modified to accommodatewhatever order is chosen for the presentation of the pictures of thesets.

FIG. 19 is a timing diagram illustrating the wave forms at variouspoints in the circuit of FIG. 16. Each wave form is given the sameidentifying numeral as that of the location where it appears in FIG. 16.The apparent delay in the line 150a in FIG. 19 represents propagationtime, and is somewhat exaggerated for purposes of clarity.

We claim:
 1. Apparatus for forming and sequentially displaying in thesame space at least two different three-dimensional images,comprising:a. intermittently operable illuminating means; b. an opticalsystem defining an optical path extending from said illuminating means;c. means supporting an array of photographs and operable to move saidphotographs successively through said optical path at a ratesufficiently greater than the human persistence of vision so that thearray moves through the path within the period of perisistence ofvision; d. means for operating said illuminating means only when one ofthe photographs is aligned with said path; e. a projection screencircumscribing an axis about which the screen is rotatable, said screenbeing curved eccentrically with respect to the axis and interceptingsaid optical path, the curvature of the screen being effective to movethe screen along the optical path toward and away from the photographsas the screen rotates; f. means synchronizing the rotation of the screenwith the operation of the illuminating means and the movement of thephotograph supporting means to project on the screen a series of imageswhich appear to an observer having persistence of vision to be athree-dimensional image;wherein the improvement comprises: g. at leasttwo series of two-dimensional photographs in said array, each seriesshowing successive sections of one of said images, the photographs ofeach series being arranged in said array in a predetermined ordercorresponding to the relationship that said successive sections bear toeach other, the photographs of each series being located in said arrayin positions different from the locations of the photographs of theother series; and h. selection means for controlling said illuminatingmeans to illuminate the photographs of only one of said series duringone movement of said array through said optical path, and to illuminatethe photographs of only another of said series during a subsequentmovement of said array through said optical path.
 2. Apparatus as inclaim 1, including:a. only two series of photographs in said array, thephotographs of one series being located alternately in said array withrespect to the photographs of the other series; and b. said selectionmeans is operable to select one or the other of said two series ofalternately located photographs.
 3. Apparatus as in claim 2, in whichsaid selection means is operable to select one series and then the otheralternately at predetermined intervals.
 4. Apparatus as in claim 3, inwhich said two series of photographs show an object having relativelymovable parts, with the parts in one position in one series and in adifferent position in the other series.
 5. Apparatus as in claim 1, inwhich:a. said photographs are of the same object having at leastrelatively two movable parts, with the parts shown in a distinctiveposition in each series; and b. said selection means is operable todisplay such series sequentially so as to produce on screen athree-dimensional illusion of movement.
 6. Apparatus as in claim 1,including means for locking said selection means to display only one ofsaid series continuously.
 7. Apparatus as in claim 1, in which saidseries of two-dimensional photographs are arranged in a film strip. 8.Apparatus for forming and displaying at least one three-dimensionalimage, comprising:a. a casing; b. intermittently operable illuminatingmeans in the casing; c. an optical system defining an optical pathextending from said illuminating means; d. means within the casingsupporting an array of photographs and operable to move the photographssuccessively through said optical path at a rate sufficiently greaterthan the human persistence of vision so that the array moves through thepath within the period of persistence of vision; e. drive means in thecasing for said supporting means, said supporting means beinginterchangeably connected to the drive means so that a differentsupporting means can be substituted with a different array ofphotographs; f. a door in the casing for access to the supporting means;and g. lock means to limit movement of the door beyond a safe distancefrom its closed position when the supporting means is moving at morethan a predetermined speed.
 9. Apparatus as in claim 8, including speedresponsive means for releasing the lock means when the drive means isbelow said predetermined speed.
 10. Apparatus as in claim 8,including:a. a brake for retarding motion of the drive means; and b.control means operated by movement of the door within said safe distanceto apply the brake to the drive means.
 11. Apparatus as in claim 10,including:a. an electric motor in said drive means; and b. means in saidbrake for energizing the motor for reverse rotation to bring it to astop quickly.
 12. Apparatus as in claim 11, including interlock means tohold the door closed until the power supply is disconnected from themotor.
 13. Apparatus as in claim 8, including:a. an electric motor foroperating the driving means; and b. means to disconnect the motor fromits source of power if there is no array of photographs on thesupporting means.
 14. Apparatus as in claim 8, including:a. means forindicating that there is no array of photographs on the supportingmeans; and b. interlock means responsive to the absence of an array onthe supporting means to activate the indicating means.